U.S. patent application number 17/720569 was filed with the patent office on 2022-07-28 for engine system.
The applicant listed for this patent is Mazda Motor Corporation. Invention is credited to Haruki Misumi, Takuma Yamagaki.
Application Number | 20220235692 17/720569 |
Document ID | / |
Family ID | 1000006316731 |
Filed Date | 2022-07-28 |
United States Patent
Application |
20220235692 |
Kind Code |
A1 |
Misumi; Haruki ; et
al. |
July 28, 2022 |
ENGINE SYSTEM
Abstract
An engine system is provided, including an engine, a circulation
system that circulates coolant through a water jacket, and a
controller. The circulation system includes a radiator passage
including a heat exchanger, a bypass passage, a flow rate control
device, and a thermally-actuated valve. The engine has a spark plug
that forcibly ignites an air-fuel mixture. The engine switches
between a first combustion in which the air-fuel mixture combusts
without the forcible ignition, and a second combustion in which the
air-fuel mixture combusts by the forcible ignition. The controller
is electrically connected to the flow rate control device, and when
the engine performs the first combustion, the controller controls
the flow rate control device to adjust the flow rate of the coolant
flowing through the water jacket according to the engine load, by
closing the radiator passage and adjusting the flow rate of the
coolant flowing through the bypass passage.
Inventors: |
Misumi; Haruki; (Aki-gun,
JP) ; Yamagaki; Takuma; (Aki-gun, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mazda Motor Corporation |
Aki-gun |
|
JP |
|
|
Family ID: |
1000006316731 |
Appl. No.: |
17/720569 |
Filed: |
April 14, 2022 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01P 2003/021 20130101;
F01P 7/16 20130101; F01P 3/02 20130101; F01P 2007/146 20130101 |
International
Class: |
F01P 7/16 20060101
F01P007/16; F01P 3/02 20060101 F01P003/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 13, 2020 |
JP |
2021-081791 |
Claims
1. An engine system, comprising: an engine having a water jacket
formed around a combustion chamber; a circulation system that is
attached to the engine and circulates coolant through the water
jacket; and a controller configured to control the circulation
system according to an operating state of the engine, wherein the
circulation system includes: a radiator passage including a heat
exchanger; a bypass passage bypassing the heat exchanger; a flow
rate control device that adjusts a flow rate of coolant flowing
through the water jacket by adjusting a flow rate of coolant
flowing through each of the radiator passage and the bypass
passage; and a thermally-actuated valve that is connected to the
radiator passage and opens to allow the coolant to pass through the
heat exchanger, wherein the engine has a spark plug that forcibly
ignites an air-fuel mixture, wherein the engine switches between a
first combustion in which the air-fuel mixture combusts without the
forcible ignition of the spark plug, and a second combustion in
which the air-fuel mixture combusts by the forcible ignition of the
spark plug, wherein the controller is electrically connected to the
flow rate control device, and wherein when the engine performs the
first combustion, the controller controls the flow rate control
device to adjust the flow rate of the coolant flowing through the
water jacket according to a load of the engine, by closing the
radiator passage and adjusting the flow rate of the coolant flowing
through the bypass passage.
2. The engine system of claim 1, wherein when the engine performs
the first combustion, the controller increases the flow rate of the
coolant flowing through the water jacket as the load increases.
3. The engine system of claim 1, wherein when the engine performs
the second combustion, the controller controls the flow rate
control device to allow the coolant to flow through each of the
radiator passage and the bypass passage.
4. The engine system of claim 2, wherein when the engine performs
the second combustion, the controller controls the flow rate
control device to allow the coolant to flow through each of the
radiator passage and the bypass passage.
5. The engine system of claim 3, wherein when the engine performs
the second combustion, the controller adjusts a temperature of the
coolant flowing through the water jacket according to the load by
adjusting the flow rate of the coolant flowing through the bypass
passage and the flow rate of the coolant flowing through the
radiator passage.
6. The engine system of claim 4, wherein when the engine performs
the second combustion, the controller adjusts a temperature of the
coolant flowing through the water jacket according to the load by
adjusting the flow rate of the coolant flowing through the bypass
passage and the flow rate of the coolant flowing through the
radiator passage.
7. The engine system of claim 5, wherein when the engine performs
the second combustion, the controller reduces the flow rate of the
coolant flowing through the bypass passage and increases the flow
rate of the coolant flowing through the radiator passage, as the
load increases.
8. The engine system of claim 6, wherein when the engine performs
the second combustion, the controller reduces the flow rate of the
coolant flowing through the bypass passage and increases the flow
rate of the coolant flowing through the radiator passage, as the
load increases.
9. The engine system of claim 1, wherein when the engine performs
the second combustion, the controller sets the flow rate of the
coolant flowing through the water jacket at a maximum flow
rate.
10. The engine system of claim 8, wherein when the engine performs
the second combustion, the controller sets the flow rate of the
coolant flowing through the water jacket at a maximum flow
rate.
11. The engine system of claim 1, wherein both when the engine
performs the first combustion and when the engine performs the
second combustion, the controller maintains a wall temperature of
the combustion chamber at a constant temperature.
12. The engine system of claim 8, wherein both when the engine
performs the first combustion and when the engine performs the
second combustion, the controller maintains a wall temperature of
the combustion chamber at a constant temperature.
13. The engine system of claim 11, wherein when the engine performs
the second combustion, the controller lowers the temperature of the
coolant flowing through the water jacket below a valve-opening
temperature of the thermally-actuated valve.
14. The engine system of claim 7, wherein in a case where the
engine performs the second combustion, when the load is below a
given load, the controller increases the flow rate of the coolant
flowing through the radiator passage to lower the temperature of
the coolant flowing through the water jacket as the load increases
and, when the load is above the given load, the controller
increases the flow rate of the coolant flowing through the radiator
passage to maintain the temperature of the coolant flowing through
the water jacket constant with respect to the load increase.
15. The engine system of claim 1, wherein the controller determines
a combustion mode of the engine at least based on an accelerator
opening detected, and controls the circulation system according to
the determined combustion mode.
16. The engine system of claim 1, wherein the flow rate control
device is installed at a location branching into the bypass passage
and the radiator passage, or a location where the bypass passage
and the radiator passage are joined, wherein the circulation system
further includes a connecting passage connecting the bypass passage
to the radiator passage, and wherein the thermally-actuated valve
opens and closes the connecting passage.
17. The engine system of claim 1, wherein the flow rate control
device is installed at a location branching into the bypass passage
and the radiator passage, or a location where the bypass passage
and the radiator passage are joined, wherein the circulation system
further includes a connecting passage bypassing the flow rate
control device and connecting the water jacket to the radiator
passage, and wherein the thermally-actuated valve opens and closes
the connecting passage.
18. The engine system of claim 14, wherein the controller
determines a combustion mode of the engine at least based on an
accelerator opening detected, and controls the circulation system
according to the determined combustion mode.
19. The engine system of claim 15, wherein the flow rate control
device is installed at a location branching into the bypass passage
and the radiator passage, or a location where the bypass passage
and the radiator passage are joined, wherein the circulation system
further includes a connecting passage connecting the bypass passage
to the radiator passage, and wherein the thermally-actuated valve
opens and closes the connecting passage.
20. The engine system of claim 15, wherein the flow rate control
device is installed at a location branching into the bypass passage
and the radiator passage, or a location where the bypass passage
and the radiator passage are joined, wherein the circulation system
further includes a connecting passage bypassing the flow rate
control device and connecting the water jacket to the radiator
passage, and wherein the thermally-actuated valve opens and closes
the connecting passage.
Description
TECHNICAL FIELD
[0001] The disclosed technology relates to an engine system.
BACKGROUND OF THE DISCLOSURE
[0002] JP2016-128652A discloses a cooling device for an engine.
This cooling device has a radiator path which circulates coolant
between the engine and a radiator, and a radiator bypass path which
bypasses the radiator and circulates the coolant. In the radiator
bypass path, an ATF warmer which warms a heater core of an
air-conditioner and lubrication oil of an automatic transmission is
disposed.
[0003] The cooling device has a rotary flow rate control valve. The
rotary flow rate control valve opens and closes the radiator path
and the radiator bypass path according to a rotational position of
a rotary valve body. Further, the rotary flow rate control valve
has a radiator path connecting passage and a thermostat valve
allocation passage. The radiator path connecting passage is
connected to the radiator path. A thermostat valve is provided to
the thermostat valve allocation passage. When opening the
thermostat valve, the coolant flows into the radiator path from the
thermostat valve allocation passage.
[0004] When the engine is warm with the coolant at a temperature
above a given temperature, the rotary flow rate control valve
rotates the rotary valve body to a rotational position where the
coolant flows into each of the radiator bypass path and the
thermostat valve allocation passage. Since the thermostat valve
opens while the engine is warm, the coolant flows into the radiator
path from the thermostat valve allocation passage.
[0005] When the temperature of the coolant further increases, the
rotary flow rate control valve rotates the rotary valve body to a
rotational position where the coolant flows to all of the radiator
bypass path, the thermostat valve allocation passage, and the
radiator path connecting passage. Further, the rotational position
of the rotary valve body is adjusted so that a flow rate of the
coolant to the radiator path increases as a temperature of the
coolant, an engine load, and/or an engine speed increase.
[0006] The combustion chamber becomes high in the temperature after
the engine has been fully warmed up. In order to cool the
combustion chamber, a passage through which the coolant cooled by
the radiator flows (a so-called "water jacket") is provided to a
part around the combustion chamber, such as a cylinder bore and a
cylinder head, which constitute the engine body, which is also
provided to the cooling device disclosed in JP2016-128652A.
[0007] Meanwhile, in the engine combustion control, the temperature
inside the combustion chamber (in-cylinder temperature) is one of
the important factors. The in-cylinder temperature requires a more
precise control as the combustion control becomes more advanced.
For example, in order to stably control compression ignition
combustion, it is necessary to accurately control the in-cylinder
temperature at a temperature higher than that of spark ignition
combustion. In addition, since the heat generated inside the
combustion chamber varies according to the engine load, the
in-cylinder temperature also varies.
[0008] In the in-cylinder temperature control, a wall temperature
of the combustion chamber is one of the important factors. It is
demanded that the wall temperature of the combustion chamber is
adjusted with good response to the change in the engine load.
[0009] The cooling device disclosed in JP2016-128652A lowers the
temperature of the coolant by increasing the flow rate of the
coolant which flows through the radiator path, when the temperature
of the coolant becomes high. When the temperature of the coolant
changes, the heat exchanging quantity between the coolant and the
combustion chamber changes. If the heat exchanging quantity is
changed according to the heat generated inside the combustion
chamber, the wall temperature of the combustion chamber can be
adjusted.
[0010] However, since the calorific capacity of the coolant is
large, it requires a long period of time to change the temperature
of the coolant. It is difficult for the temperature adjustment of
the coolant to adjust the wall temperature of the combustion
chamber with good response to the change in the engine load.
SUMMARY OF THE DISCLOSURE
[0011] The technology disclosed herein adjusts a wall temperature
of a combustion chamber with high response according to a load of
an engine.
[0012] The present inventers have completed the technology
disclosed herein by paying attention to the adjustment of the wall
temperature of the combustion chamber by changing a flow rate of
coolant which flows through a water jacket to change a heat
transfer coefficient between the coolant and the combustion
chamber, without changing a temperature of the coolant.
[0013] According to one aspect of the present disclosure, an engine
system is provided, which includes an engine having a water jacket
formed around a combustion chamber, a circulation system that is
attached to the engine and circulates coolant through the water
jacket, and a controller configured to control the circulation
system according to an operating state of the engine. The
circulation system includes a radiator passage including a heat
exchanger, a bypass passage bypassing the heat exchanger, a flow
rate control device that adjusts a flow rate of coolant flowing
through the water jacket by adjusting a flow rate of coolant
flowing through each of the radiator passage and the bypass
passage, and a thermally-actuated valve that is connected to the
radiator passage and opens to allow the coolant to pass through the
heat exchanger. The engine has a spark plug that forcibly ignites
an air-fuel mixture, and switches between a first combustion in
which the air-fuel mixture combusts without the forcible ignition
of the spark plug, and a second combustion in which the air-fuel
mixture combusts by the forcible ignition of the spark plug. The
controller is electrically connected to the flow rate control
device. When the engine performs the first combustion, the
controller controls the flow rate control device to adjust the flow
rate of the coolant flowing through the water jacket according to a
load of the engine, by closing the radiator passage and adjusting
the flow rate of the coolant flowing through the bypass
passage.
[0014] According to this configuration, the coolant passing through
the water jacket of the engine exchanges heat with the combustion
chamber. The coolant circulates through the water jacket by the
circulation system.
[0015] The circulation system includes the thermally-actuated valve
which opens when the coolant reaches a given temperature. When the
thermally-actuated valve opens, part of the coolant passes through
the heat exchanger, and thus, a coolant temperature decreases. By
the thermally-actuated valve, the coolant temperature is maintained
at a specific temperature corresponding to a valve-opening
temperature of the thermally-actuated valve.
[0016] When the engine performs the first combustion, the flow rate
control device closes the radiator passage, and thus the coolant
flows through the bypass passage. Further, the flow rate control
device adjusts the flow rate of the coolant. Therefore, the flow
rate of the coolant which flows through the water jacket changes.
The flow rate of the coolant can be changed by the flow rate
control device more promptly compared with the temperature of the
coolant. Thus, the flow rate control device can adjust the flow
rate of the coolant which flows through the water jacket with high
response to the change of the load.
[0017] As the flow rate of the coolant which flows through the
water jacket becomes lower, the heat transfer coefficient
decreases, whereas, as the flow rate of the coolant which flows
through the water jacket increases, the heat transfer coefficient
increases. The heat generated inside the combustion chamber changes
according to the engine load. Therefore, since the controller
changes, through the flow rate control device, the flow rate of the
coolant which flows through the water jacket according to the
engine load, the engine system can adjust a wall temperature of the
combustion chamber with high response.
[0018] When the engine performs the first combustion, the
controller may increase the flow rate of the coolant flowing
through the water jacket as the load increases.
[0019] As the engine load increases, the heat generated inside the
combustion chamber also increases. As the load increases, the flow
rate of the coolant flowing through the water jacket increases, and
thus, the heat transfer coefficient increases. The wall temperature
of the combustion chamber is maintained at the suitable
temperature.
[0020] When the engine performs the second combustion, the
controller may control the flow rate control device to allow the
coolant to flow through each of the radiator passage and the bypass
passage.
[0021] When the engine performs the second combustion (that is,
when the air-fuel mixture combusts by the forcible ignition of the
spark plug), the thermal efficiency drops compared with when
performing the first combustion. The amount of heat released to the
wall part of the combustion chamber increases. When the engine
performs the second combustion, the controller allows the coolant
to flow through each of the radiator passage and the bypass
passage, through the flow rate control device. For example, by
increasing the flow rate of the coolant flowing through the
radiator passage, the coolant temperature is reduced. When the
engine performs the second combustion, the wall temperature of the
combustion chamber becomes suitable.
[0022] When the engine performs the second combustion, the
controller may adjust the temperature of the coolant flowing
through the water jacket according to the load by adjusting the
flow rate of the coolant flowing through the bypass passage and the
flow rate of the coolant flowing through the radiator passage.
[0023] When the flow rate of the coolant flowing through the
radiator passage increases, the coolant temperature decreases.
Although when the load becomes high, the heat generated inside the
combustion chamber increases, by the temperature of the coolant
flowing through the water jacket being adjusted according to the
load, the wall temperature of the combustion chamber becomes
suitable.
[0024] When the engine performs the second combustion, the
controller may reduce the flow rate of the coolant flowing through
the bypass passage and increase the flow rate of the coolant
flowing through the radiator passage, as the load increases.
[0025] When the flow rate of the coolant flowing through the
radiator passage increases, the coolant temperature decreases. By
reducing the coolant temperature when the load is high and the heat
generated inside the combustion chamber is also high, the wall
temperature of the combustion chamber becomes suitable. On the
other hand, when the flow rate of the coolant flowing through the
radiator passage decreases, the coolant temperature increases. By
increasing the coolant temperature when the load is low and the
heat generated inside the combustion chamber is low, the wall
temperature of the combustion chamber becomes suitable.
[0026] When the engine performs the second combustion, the
controller may set the flow rate of the coolant flowing through the
water jacket at a maximum flow rate.
[0027] When the engine performs the second combustion, the amount
of heat released to the wall part of the combustion chamber
increases. By making the flow rate of the coolant flowing through
the water jacket the maximum flow rate, the wall temperature of the
combustion chamber becomes suitable when the engine performs the
second combustion.
[0028] Both when the engine performs the first combustion and when
the engine performs the second combustion, the controller may
maintain the wall temperature of the combustion chamber at a
constant temperature.
[0029] The ideal wall temperature of the combustion chamber when
the engine performs the first combustion, does not necessarily
match with the ideal wall temperature of the combustion chamber
when the engine performs the second combustion. When the engine
performs the first combustion, since the air-fuel mixture combusts
by self-ignition, the wall temperature of the combustion chamber is
preferable to be high in view of stabilizing the ignition. On the
other hand, when the engine performs the second combustion, if the
wall temperature of the combustion chamber is excessively high,
abnormal combustion, such as knocking, may occur. Therefore,
changing the wall temperature of the combustion chamber according
to the switching of the combustion mode is ideal. However, since
the calorific capacity of the wall part of the combustion chamber
is large, it is difficult to change the temperature of the wall
part of the combustion chamber in a short period of time.
[0030] According to this configuration, both when the engine
performs the first combustion and when the engine performs the
second combustion, the wall temperature of the combustion chamber
is maintained at a permissible specific temperature. More
specifically, when the engine performs the first combustion, while
maintaining the coolant temperature constant by using the
thermally-actuated valve, the flow rate of the coolant which flows
through the water jacket is adjusted according to the load, and
therefore, the wall temperature of the combustion chamber can be
maintained at the specific temperature. On the other hand, when the
engine performs the second combustion, by adjusting the flow rate
of the coolant which flows through the bypass passage and the flow
rate of the coolant which flows through the radiator passage so
that the temperature of the coolant which flows through the water
jacket is adjusted according to the load, the wall temperature of
the combustion chamber can be maintained at the same specific
temperature. As a result, even when the combustion mode changes,
the wall temperature of the combustion chamber becomes
suitable.
[0031] When the engine performs the second combustion, the
controller may lower the temperature of the coolant flowing through
the water jacket below a valve-opening temperature of the
thermally-actuated valve.
[0032] When the engine performs the second combustion, the amount
of heat released to the wall part of the combustion chamber
increases. By relatively lowering the temperature of the coolant
flowing through the water jacket when the engine performs the
second combustion, the wall temperature of the combustion chamber
becomes suitable.
[0033] When the engine performs the first combustion, the amount of
heat released to the wall part of the combustion chamber decreases.
When the engine performs the first combustion, the coolant
temperature is defined by the valve-opening temperature of the
thermally-actuated valve as described above. By setting the
valve-opening temperature of the thermally-actuated valve at the
relatively high temperature, the temperature of the coolant flowing
through the water jacket relatively increases, and thus, the wall
temperature of the combustion chamber becomes suitable.
[0034] In a case where the engine performs the second combustion,
when the load is below a given load, the controller may increase
the flow rate of the coolant flowing through the radiator passage
to lower the temperature of the coolant flowing through the water
jacket as the load increases and, when the load is above the given
load, the controller may increase the flow rate of the coolant
flowing through the radiator passage to maintain the temperature of
the coolant flowing through the water jacket constant with respect
to the load increase.
[0035] When the load is lower than the given load, the temperature
of the coolant flowing through the water jacket decreases as the
load increases. The wall temperature of the combustion chamber can
be maintained at a constant temperature with respect to the load
increase. When the load is above the given load, the temperature of
the coolant flowing through the water jacket becomes constant as
the load increases. The wall temperature of the combustion chamber
becomes suitable.
[0036] The controller may determine a combustion mode of the engine
at least based on an accelerator opening detected, and control the
circulation system according to the determined combustion mode.
[0037] The combustion mode of the engine may be determined
according to at least the accelerator opening, in other words,
according to the engine load.
[0038] The flow rate control device may be installed at a location
branching into the bypass passage and the radiator passage, or a
location where the bypass passage and the radiator passage are
joined. The circulation system may further have a connecting
passage connecting the bypass passage to the radiator passage. The
thermally-actuated valve may open and close the connecting
passage.
[0039] According to this configuration, while the radiator passage
is closed, when the coolant temperature increases and the
thermally-actuated valve opens, the coolant flows to the radiator
passage from the bypass passage. Thus, the coolant temperature
decreases. By the thermally-actuated valve, the coolant temperature
can be maintained at the given temperature.
[0040] The flow rate control device may be installed at a location
branching into the bypass passage and the radiator passage, or a
location where the bypass passage and the radiator passage are
joined. The circulation system may further have a connecting
passage bypassing the flow rate control device and connecting the
water jacket to the radiator passage. The thermally-actuated valve
may open and close the connecting passage.
[0041] According to this configuration, while the radiator passage
is closed by the flow rate control device, when the coolant
temperature increases and the thermally-actuated valve opens, the
coolant bypasses the flow rate control device and flows to the
radiator passage. Thus, the coolant temperature decreases. Also in
this case, by the thermally-actuated valve, the coolant temperature
can be maintained at the given temperature.
[0042] The flow rate control device may include a housing provided
with a first port that is connected to the bypass passage, a second
port that is connected to the radiator passage, and a third port
that communicates with each of the first port and the second port.
The flow rate control device may include a rotary valve body
rotatably accommodated in the housing, intervening between the
first port, the second port and the third port, and having a first
water flow opening that communicates with the first port and a
second water flow opening that communicates with the second port.
The flow rate control device may further include an actuator that
rotates the rotary valve body to change openings of the first water
flow opening and the second water flow opening so as to adjust the
flow rate of the coolant which flows through each of the first port
and the second port.
[0043] The flow rate control device having the rotary valve body
can selectively close the bypass passage and/or the radiator
passage, and can adjust the flow rate of the bypass passage and the
flow rate of the radiator passage. The engine system provided with
the flow rate control device can realize the flow rate adjustment
of the water jacket described above with the simple
configuration.
BRIEF DESCRIPTION OF DRAWINGS
[0044] FIG. 1 illustrates an exemplary engine system.
[0045] FIG. 2 is a block diagram of the exemplary engine
system.
[0046] FIG. 3 illustrates an exemplary control map of the engine
system.
[0047] FIG. 4 illustrates an exemplary circulation system.
[0048] FIG. 5 illustrates an exemplary flow rate control
device.
[0049] FIG. 6 illustrates an exemplary control of the circulation
system.
[0050] FIG. 7 illustrates an exemplary control of the circulation
system.
[0051] FIG. 8 illustrates an exemplary control procedure of the
circulation system.
[0052] FIG. 9 illustrates an exemplary control procedure of the
circulation system.
[0053] FIG. 10 illustrates an exemplary circulation system.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0054] Hereinafter, one embodiment of an engine system is described
with reference to the accompanying drawings. The engine system
described herein is merely illustration.
(Example Configuration of Engine System)
[0055] FIGS. 1 and 2 illustrate one example of a configuration of
an engine system 1. The engine system 1 is mounted on an
automobile. The engine system 1 is provided with an engine 10 which
is an internal combustion engine. When the engine 10 operates, the
automobile travels. Note that the automobile may be an automobile
on which only the engine 10 is mounted as a propelling power
source, or may be a hybrid vehicle on which the engine 10 and an
electric motor are mounted.
[0056] The engine 10 is provided with a cylinder block 11 and a
cylinder head 12. A plurality of cylinders 13 are formed in the
cylinder block 11. The engine 10 is a multi-cylinder engine.
[0057] The plurality of cylinders 13 are lined up along a
crankshaft 14 (also see FIG. 4). A piston 15 is inserted in each
cylinder 13. The piston 15 is coupled to the crankshaft 14 via a
connecting rod 151. The piston 15, the cylinder 13, and the
cylinder head 12 form a combustion chamber 16.
[0058] An intake port 121 which communicates with each cylinder 13
is formed in the cylinder head 12. An intake valve 122 disposed at
the intake port 121 opens and closes the intake port 121. An intake
valve operating mechanism 123 (see FIG. 2) opens and closes the
intake valve 122 at a given timing. The intake valve operating
mechanism 123 is a variable valve operating mechanism which can
vary a valve timing and/or a valve lift.
[0059] An exhaust port 124 which communicates with each cylinder 13
is formed in the cylinder head 12. An exhaust valve 125 disposed at
the exhaust port 124 opens and closes the exhaust port 124. An
exhaust valve operating mechanism 126 opens and closes the exhaust
valve 125 at a given timing. The exhaust valve operating mechanism
126 is a variable valve operating mechanism which can vary a valve
timing and/or a valve lift.
[0060] An injector 131 is attached to the cylinder head 12 for
every cylinder 13. The injector 131 injects fuel directly into the
cylinder 13. A spark plug 132 is attached to the cylinder head 12
for every cylinder 13. The spark plug 132 forcibly ignites an
air-fuel mixture inside the cylinder 13.
[0061] An intake passage 17 is connected to one side surface of the
engine 10. The intake passage 17 communicates with the intake port
121. A throttle valve 171 is disposed at the intake passage 17. The
throttle valve 171 adjusts an introducing amount of air into the
cylinder 13. An exhaust passage 18 is connected to the other side
surface of the engine 10. The exhaust passage 18 communicates with
the exhaust port 124.
[0062] An exhaust gas recirculation (EGR) passage 19 is connected
between the intake passage 17 and the exhaust passage 18. The EGR
passage 19 recirculates part of exhaust gas to the intake passage
17. An EGR cooler 191 is disposed at the EGR passage 19. The EGR
cooler 191 cools the exhaust gas. An EGR valve 192 is disposed at
the EGR passage 19. The EGR valve 192 adjusts a flow rate of
exhaust gas which flows through the EGR passage 19.
[0063] The engine system 1 is provided with an ECU (Engine Control
Unit) 100 for operating the engine 10. The ECU 100 is a controller
based on a well-known microcomputer, which includes a CPU (Central
Processing Unit) 101, memory 102, and an I/F (interface) circuit
103. The CPU 101 executes a program. The memory 102 is, for
example, comprised of RAM (Random Access Memory) and/or ROM (Read
Only Memory), and stores the program and data. The I/F circuit 103
inputs and outputs an electric signal. The ECU 100 is one example
of a controller.
[0064] The ECU 100 is connected to various kinds of sensors
SN1-SN5. The sensors SN1-SN5 output signals to the ECU 100. The
sensors include the following sensors:
[0065] First water temperature sensor SN1: It outputs a signal
corresponding to a temperature of coolant which flows into the
engine 10, in a circulation system 91 of the coolant (described
later);
[0066] Second water temperature sensor SN2: It is attached to the
engine 10, and outputs a signal corresponding to a temperature of
coolant which flows inside the engine 10;
[0067] In-cylinder pressure sensor SN3: It is attached to the
cylinder head 12, and outputs a signal corresponding to a pressure
inside each cylinder 13;
[0068] Crank angle sensor SN4: It is attached to the engine 10, and
outputs a signal corresponding to a rotation angle of the
crankshaft 14; and
[0069] Accelerator opening sensor SN5: It is attached to an
accelerator pedal mechanism, and outputs a signal corresponding to
an operating amount of the accelerator pedal.
[0070] The ECU 100 determines an operating state of the engine 10
based on the signals from the sensors SN1-SN5, and then calculates
a controlled variable of each device according to control logic
defined beforehand. The control logic is stored in the memory 102.
The control logic includes calculating targeted amounts and/or
controlled variables by using a map stored in the memory 102. The
ECU 100 outputs electric signals according to the calculated
controlled variables to the injector 131, the spark plug 132, the
intake valve operating mechanism 123, the exhaust valve operating
mechanism 126, the throttle valve 171, the EGR valve 192, and a
coolant control valve 4 (described later).
[0071] In more detail, the ECU 100 has a load calculating module
104, a combustion mode determining module 105, a water temperature
determining module 106, and a CCV controlling module 107 executed
by the CPU 101 to perform their respective functions. These modules
are stored in the memory 102 as software modules.
[0072] The load calculating module 104 calculates a target load of
the engine 10 based on the output signal of the accelerator opening
sensor SN5. The combustion mode determining module 105 determines
an operating range of the engine 10 in a base map 301 (described
later, see FIG. 3) based on the load of the engine 10 and the
output signal of the crank angle sensor SN4, and determines a
combustion mode corresponding to the operating range. The water
temperature determining module 106 determines a temperature of
coolant which flows through a water jacket 20 (see FIG. 4) around
the combustion chamber 16 based on the output signal of the second
water temperature sensor SN2. The CCV controlling module 107 cools
the engine 10 by controlling the coolant control valve 4 according
to the operating state of the engine 10.
(Engine Operation Control Map)
[0073] FIG. 3 illustrates the base map 301 according to the control
of the engine 10. The base map 301 is stored in the memory 102 of
the ECU 100. The illustrated base map 301 is for a case of the
engine 10 being fully warmed up.
[0074] The base map 301 is defined by the load and engine speed of
the engine 10. The base map 301 is roughly divided into four ranges
according to the load and the engine speed. In more detail, a first
range 311 includes a range from the low load to high load at a high
speed, and a range of the high load at a low speed and a middle
speed. A second range 312 is a low-load range at the low speed and
the middle speed. A third range 313 is a range from the low load to
the middle load at the low speed and the middle speed. A fourth
range 314 is a range from the middle load to the high load at the
low speed and the middle speed. Note that the low-speed range, the
middle-speed range, and the high-speed range may be a low-speed
range, a middle-speed range, and a high-speed range when the entire
operating range of the engine 10 is divided in the engine speed
direction into three substantially equal ranges.
[0075] Next, operation of the engine 10 in each range is briefly
described. The ECU 100 determines the operating range according to
the target load for the engine 10 and the engine speed of the
engine 10, and the ECU 100 changes the open-and-close operation of
the intake valve 122 and the exhaust valve 125, the fuel injection
timing, and the existence of the forcible ignition, according to
the determined operating range. Therefore, the combustion mode of
the engine 10 changes between SI (Spark Ignition) combustion, HCCI
(Homogeneous Charge Compression Ignition) Combustion, MPCI
(Multiple Premixed fuel injection Compression Ignition) combustion,
and SPCCI (Spark Controlled Compression Ignition) combustion.
(SI Combustion)
[0076] When the operating state of the engine 10 is in the first
range 311, the ECU 100 carries out flame propagation combustion of
the air-fuel mixture inside the cylinder 13. The intake valve
operating mechanism 123 opens the intake valve 122 at a given
timing and/or by a given lift, and the exhaust valve operating
mechanism 126 opens the exhaust valve 125 at a given timing and/or
by a given lift. The injector 131 injects fuel into the cylinder 13
during an intake stroke and/or a compression stroke. The spark plug
132 ignites the air-fuel mixture near a compression top dead
center.
(HCCI Combustion)
[0077] When the operating state of the engine 10 is in the second
range 312, the ECU 100 carries out compression ignition combustion
of the air-fuel mixture inside the cylinder 13. The intake valve
operating mechanism 123 opens the intake valve 122 at a given
timing and/or by a given lift, and the exhaust valve operating
mechanism 126 opens the exhaust valve 125 at a given timing and/or
by a given lift. The injector 131 injects fuel into the cylinder 13
during an intake stroke. The spark plug 132 does not ignite the
air-fuel mixture. The air-fuel mixture carries out compression
self-ignition and combusts near a compression top dead center.
(MPCI Combustion)
[0078] When the operating state of the engine 10 is in the third
range 313, the ECU 100 carries out compression ignition combustion
of the air-fuel mixture inside the cylinder 13. The intake valve
operating mechanism 123 opens the intake valve 122 at a given
timing and/or by a given lift, and the exhaust valve operating
mechanism 126 opens the exhaust valve 125 at a given timing and/or
by a given lift. The injector 131 injects fuel into the cylinder 13
during an intake stroke and a compression stroke. The injector 131
performs a divided injection. The spark plug 132 does not ignite
the air-fuel mixture. The air-fuel mixture carries out compression
self-ignition and combusts near a compression top dead center.
[0079] By the divided injection, the air-fuel mixture inside the
cylinder 13 becomes heterogeneous. In this regard, the MPCI
combustion differs from the HCCI combustion in which a homogeneous
air-fuel mixture is formed. The MPCI combustion allows a control of
a timing of the compression self-ignition when the load of the
engine 10 is relatively high.
(SPCCI Combustion)
[0080] When the operating state of the engine 10 is in the fourth
range 314, the ECU 100 carries out flame propagation combustion of
part of the air-fuel mixture inside the cylinder 13, and carries
out compression ignition combustion of the remaining air-fuel
mixture. The intake valve operating mechanism 123 opens the intake
valve 122 at a given timing and/or by a given lift, and the exhaust
valve operating mechanism 126 opens the exhaust valve 125 at a
given timing and/or by a given lift. The injector 131 injects fuel
into the cylinder 13 during a compression stroke. The spark plug
132 ignites the air-fuel mixture near a compression top dead
center. The air-fuel mixture starts flame propagation combustion.
The temperature inside the cylinder 13 becomes high due to
generation of combustion heat, and the pressure inside the cylinder
13 increases due to flame propagation. Accordingly, unburnt mixture
gas carries out, for example, compression self-ignition after a
compression top dead center to start combustion. The flame
propagation combustion and the compression ignition combustion
progress in parallel after the compression ignition combustion is
started.
(Configuration of Circulation System)
[0081] Next, a configuration of the circulation system 91 which the
engine system 1 has is described with reference to FIG. 4. The
circulation system 91 is a device which is attached to the engine
10 and circulates the coolant through the water jacket 20.
[0082] The water jacket 20 is formed inside the engine 10. The
water jacket 20 constitutes a circuit which is connected to the
circulation system 91 and through which the coolant is circulated
as well as the circulation system 91. The water jacket 20 has an
in-block jacket 21 and an in-head jacket 22. The in-block jacket 21
is formed in the cylinder block 11 so that it spreads along the
outer circumference of each cylinder 13.
[0083] The in-head jacket 22 is formed in the cylinder head 12. The
in-head jacket 22 communicates with the in-block jacket 21 (see
broken lines in FIG. 4). The in-head jacket 22 has a first jacket
22a and a second jacket 22b. The first jacket 22a and the second
jacket 22b are independent from each other.
[0084] The first jacket 22a is formed so that it extends along an
upper part of a plurality of lined-up combustion chambers 16. The
coolant which flows through the first jacket 22a mainly exchanges
heat (mainly, cools) with the combustion chamber 16. In detail, the
coolant which flows through the first jacket 22a exchanges heat
with the atmosphere inside the combustion chamber 16 via a wall
surface of the combustion chamber 16.
[0085] The second jacket 22b is formed so that it extends along a
circumference part of the exhaust ports 124 of the plurality of
lined-up cylinders 13. The coolant which flows through the second
jacket 22b mainly exchanges heat (mainly, cools) with the exhaust
port 124 where hot exhaust gas flows.
[0086] A water pump 3 is installed in the cylinder block 11, at an
end of the engine 10 (inflow-side end part 10a). The water pump 3
constitutes a part of the circulation system 91.
[0087] The water pump 3 is a mechanical pump in which a rotation
shaft of the pump is connected with the crankshaft 14 of the engine
10 via a pulley, a belt, etc. The water pump 3 operates by a
driving force of the engine 10. Note that the water pump 3 may be
an electric rotary pump which can operate independently from the
engine 10.
[0088] The in-block jacket 21 is connected with a discharge port 3a
of the water pump 3 via a coolant introducing passage 23.
Therefore, the coolant discharged from the water pump 3 flows into
the in-block jacket 21 through the coolant introducing passage 23.
The coolant which flowed into the in-block jacket 21 flows into the
in-head jacket 22. In detail, it dividedly flows into the first
jacket 22a and the second jacket 22b.
[0089] The coolant control valve (CCV) 4 (an example of a "flow
rate control device" in the disclosed art) is installed in the
cylinder head 12, at an end (outflow-side end part 10b) opposite
from the inflow-side end part 10a of the engine 10. The coolant
control valve 4 constitutes a part of the circulation system
91.
[0090] A third port 65 (see FIG. 5) of the coolant control valve 4
is connected with the first jacket 22a via a first coolant deriving
passage 24. Therefore, the coolant which flows through the first
jacket 22a flows out of the engine 10 through the first coolant
deriving passage 24, and flows into the coolant control valve 4
(the details of the coolant control valve 4 will be described
later).
[0091] A second coolant deriving passage 25 which communicates with
the second jacket 22b is formed in a part of the outflow-side end
part 10b, on the exhaust side of the cylinder head 12. Therefore,
the coolant which flows through the second jacket 22b flows out of
the engine 10 through the second coolant deriving passage 25, and
flows into a second circulation flow passage 31 (described
later).
[0092] A third coolant deriving passage 26 which communicates with
the in-block jacket 21 is formed in a part of the outflow-side end
part 10b, on the intake side of the cylinder block 11. Therefore,
part of the coolant which flows through the in-block jacket 21
flows out of the engine 10 through the third coolant deriving
passage 26, and flows into a third circulation flow passage 41
(described later).
[0093] The circulation system 91 includes, in addition to the water
pump 3 and the coolant control valve 4 which are described above, a
radiator 27 (an example of a "heat exchanger" in the disclosed
art), and a thermally-actuated valve (thermostat valve) 28.
Further, the engine system 1 including the circulation system 91
roughly includes, as passages through which the coolant is
circulated, a second circuit 30, a third circuit 40, and a first
circuit 50.
(Second Circuit)
[0094] The second circuit 30 has the second circulation flow
passage 31 which is provided with a passage which branches into two
(a first branch passage 31a and a second branch passage 31b). In
the first branch passage 31a, the EGR cooler 191 and a heater 71
are disposed. The heater 71 is built into an air-conditioner which
adjusts air inside a vehicle cabin. In the second branch passage
31b, the throttle valve (Electric Throttle Body: ETB) 171 and the
EGR valve 192 are disposed. An upstream end of the second
circulation flow passage 31 is connected to the second coolant
deriving passage 25. A downstream end of the second circulation
flow passage 31 is connected to a suction port 3b of the water pump
3 in a state where it is joined to the first circuit 50 and the
third circuit 40.
[0095] Inside of the engine 10, the in-block jacket 21, the second
jacket 22b, and the second coolant deriving passage 25 constitute a
passage of the second circuit 30. Therefore, in the second circuit
30, coolant which flowed through the in-block jacket 21 and the
second jacket 22b among the coolant discharged from the water pump
3 dividedly flows into the first branch passage 31a and the second
branch passage 31b. Then, it returns to the water pump 3 after
being joined.
[0096] The coolant which flows through the second circuit 30
exchanges heat with the engine 10 (mainly, with the exhaust port
124). Further, it also exchanges heat with the EGR cooler 191, the
heater 71, the throttle valve 171, and the EGR valve 192.
(Third Circuit)
[0097] The third circuit 40 has the third circulation flow passage
41 in which an oil cooler 72 and an automatic transmission fluid
(ATF) heat exchanger 73 are installed. The oil cooler 72 is
installed in a system which circulates and supplies lubricating oil
to the engine 10. The ATF heat exchanger 73 is installed in a
system which circulates and supplies hydraulic fluid of an
automatic transmission. An upstream end of the third circulation
flow passage 41 is connected to the third coolant deriving passage
26. A downstream end of the third circulation flow passage 41 is
connected to the suction port 3b of the water pump 3 in a state
where it is joined to the first circuit 50 and the second circuit
30.
[0098] Inside of the engine 10, the in-block jacket 21 and the
third coolant deriving passage 26 constitute a passage of the third
circuit 40. Therefore, in the third circuit 40, among the coolant
discharged from the water pump 3, part of the coolant which flows
through the in-block jacket 21 flows through the third circulation
flow passage 41 and returns to the water pump 3. The coolant which
flows through the third circuit 40 exchanges heat with the oil
cooler 72 and the ATF heat exchanger 73.
(First Circuit)
[0099] The first circuit 50 has a bypass passage 51, a connecting
passage 52, and a radiator passage 53. Inside of the engine 10, the
in-block jacket 21, the first jacket 22a, and the first coolant
deriving passage 24 constitute a passage of the first circuit
50.
[0100] The passage of the first circuit 50 branches to the bypass
passage 51 and the radiator passage 53 at the coolant control valve
4. The downstream ends of the bypass passage 51 and the radiator
passage 53 are connected to the suction port 3b of the water pump 3
in a state where they are joined to the second circuit 30 and the
third circuit 40.
[0101] The radiator 27 is provided to the radiator passage 53. The
radiator 27 is installed behind a front grille of the automobile.
The coolant which flows through the radiator 27 exchanges heat
mainly with outside air flow caused by the automobile traveling.
The coolant radiates the heat and is cooled by flowing through the
radiator passage 53.
[0102] Therefore, the radiator passage 53 cools, by the radiator
27, the coolant which is discharged from the water pump 3 and is
heated by exchanging heat while flowing through the in-block jacket
21 and the first jacket 22a, and recirculates it to the in-block
jacket 21 and the first jacket 22a.
[0103] The bypass passage 51 is a passage which bypasses the
radiator passage 53. The bypass passage 51 is shorter than the
radiator passage 53. Only the thermally-actuated valve 28 is
provided to the bypass passage 51. The thermally-actuated valve 28
is connected by the radiator passage 53 via the connecting passage
52 in a state where the upstream side and the downstream side of
the bypass passage 51 always communicate with each other.
[0104] Therefore, the bypass passage 51 recirculates to the
in-block jacket 21 and the first jacket 22a the coolant which was
discharged from the water pump 3 and exchanged heat while flowing
through the in-block jacket 21 and the first jacket 22a, without
cooling the coolant by the radiator 27.
[0105] The thermally-actuated valve 28 is a known device which
opens and closes at a high temperature set beforehand. The
thermally-actuated valve 28 has a valve body which is biased in a
closing direction by an elastic force of a spring. The
thermally-actuated valve 28 opens and closes by the valve body
being displaced according to an action of wax. The
thermally-actuated valve 28 of the engine system 1 is set so that
its valve-opening temperature is higher than a valve-opening
temperature of a conventional thermally-actuated valve.
[0106] When the thermally-actuated valve 28 opens, the bypass
passage 51 communicates the radiator passage 53 via the connecting
passage 52. Therefore, when the thermally-actuated valve 28 opens,
part of the coolant which flows through the bypass passage 51
passes through the connecting passage 52, and flows into the
radiator passage 53.
(Coolant Control Valve)
[0107] FIG. 5 illustrates the coolant control valve 4. The coolant
control valve 4 is a valve which can adjust a flow rate of the
coolant, and is comprised of a housing 60, a rotary valve body 61,
and an actuator 62.
[0108] A cylindrical flow-dividing chamber 60a is provided inside
the housing 60. The cylindrical rotary valve body 61 is rotatably
accommodated in the flow-dividing chamber 60a. A first port 63 and
a second port 64 are formed in the housing 60 so that they extend
radially outward from a given position in an outer circumference of
the flow-dividing chamber 60a. The first port 63 is connected to
the bypass passage 51. The second port 64 is connected to the
radiator passage 53.
[0109] One end of the flow-dividing chamber 60a is opened. This
opening constitutes the third port 65 through which the coolant
flows into the flow-dividing chamber 60a. Further, the housing 60
is attached to the cylinder head 12 so that the third port 65 is
coaxially connected to the first coolant deriving passage 24.
Therefore, a circumferential wall of the rotary valve body 61
intervenes between the third port 65 and each of the first port 63
and the second port 64.
[0110] A first water flow opening 61a and a second water flow
opening 61b are formed at given positions of the circumferential
wall of the rotary valve body 61. The first water flow opening 61a
has a length in the circumferential direction longer than the
second water flow opening 61b, and has a relatively large opening
area. Depending on the rotational position of the rotary valve body
61, the third port 65 communicates or does not communicate with the
first port 63 and the second port 64 via the first water flow
opening 61a and the second water flow opening 61b, respectively.
Further, when communicating with the ports, an opening between each
of the first port 63 and the second port 64 and the third port 65
varies depending on the rotational position of the rotary valve
body 61.
[0111] The other end of the flow-dividing chamber 60a is sealed
with a closure wall 66. The actuator 62 is accommodated inside the
housing 60, on the opposite side of the flow-dividing chamber 60a
with respect to the closure wall 66. A rotation shaft 62a of the
actuator 62 projects into the flow-dividing chamber 60a through a
shaft hole which opens at the center of the closure wall 66. The
rotary valve body 61 is attached via support arms 62b to the
rotation shaft 62a projected into the flow-dividing chamber 60a.
The ECU 100 outputs a control signal to the actuator 62. By the ECU
100 controlling the actuator 62, the rotary valve body 61 is
rotated.
[0112] Returning to FIG. 4, the first water temperature sensor SN1
is disposed at a passage where the first circuit 50, the second
circuit 30, and the third circuit 40 join and flow into the water
pump 3. The second water temperature sensor SN2 is disposed at the
first jacket 22a. The first water temperature sensor SN1 measures a
temperature of coolant which flows into the engine 10. The second
water temperature sensor SN2 measures a temperature of coolant
which flows into the water jacket 20 (more accurately, into the
first jacket 22a). These sensors SN1 and SN2 are utilized for a
coolant control and a combustion control. For example, when
performing the advanced combustion control, the second water
temperature sensor SN2 is utilized for estimating the wall
temperature of the combustion chamber 16. The second water
temperature sensor SN2 is utilized for controlling the actuator
62.
[0113] In this circulation system 91, the ECU 100 controls the
coolant control valve 4 based on the measurement of the second
water temperature sensor SN2. This adjusts a flow rate of the
coolant which flows through the first circuit 50 (i.e., the bypass
passage 51 and the radiator passage 53). Note that the flow of the
coolant in the connecting passage 52 is automatically adjusted by
the thermally-actuated valve 28.
[0114] The coolant which flows through the circulation system 91 is
mainly cooled by the radiator 27 installed in the radiator passage
53. The temperature of the coolant is adjusted.
[0115] That is, the main object of the circulation system 91 is the
first circuit 50. The flow rate and the temperature of the coolant
in each of the second circuit 30 and the third circuit 40 change
according to an adjustment of the flow rate and the temperature of
the coolant in the first circuit 50. In this circulation system 91,
although the first circuit 50 is essential, the second circuit 30
and the third circuit 40 are not essential.
(How Coolant Flows)
[0116] As described above, the coolant which flows through the
first jacket 22a mainly exchanges heat with the wall part of the
combustion chamber 16 to cool the wall part of the combustion
chamber 16. In this engine system 1, a plurality of ways for the
coolant to flow are set according to the temperature of the coolant
which flows through the first jacket 22a (the measurement of the
second water temperature sensor SN2) in order to stably and
efficiently perform the combustion control of the engine 10. FIG. 6
illustrates a flowing state of each circuit in the engine system 1
according to the temperature of the coolant.
[0117] In the coolant control valve 4, the actuator 62 is
controlled to adjust the flow rate of the coolant which flows
through both the first port 63 and the second port 64. That is, the
opening of each of the first water flow opening 61a and the second
water flow opening 61b is changed so that the rotary valve body 61
is at the given rotational position.
[0118] "Low Temperature" is a so-called state during "cold start,"
such as immediately after the engine 10 is started. "Low
Temperature" is a state where a temperature t of the coolant which
flows through the first jacket 22a is below a first switching
temperature t11 (for example, 40.degree. C.). "Full Warm-up" is a
state where the engine 10 is warmed up to a temperature suitable
for operation, and is a so-called state after "warmed up." "Full
Warm-up" is a state where the temperature t of the coolant which
flows through the first jacket 22a is at or above a second
switching temperature t12 (for example, 80.degree. C.). "Half
Warm-up" is a state between "Low Temperature" and "Full Warm-up"
(i.e., it is a transition state). "Half Warm-up" is a state where
the temperature t of the coolant which flows through the first
jacket 22a is at or above the first switching temperature t11 and
below the second switching temperature t12, and it is a state where
the coolant temperature t is from 40.degree. C. to 80.degree.
C.
[0119] As illustrated by a left state 81 in FIG. 6, the coolant
neither flows into the bypass passage 51 nor the radiator passage
53 during "Low Temperature" (both the flow rates are zero). That
is, in the first circuit 50, the circulation of the coolant is not
performed. At this time, in the coolant control valve 4, the rotary
valve body 61 is set at a rotational position where both the first
port 63 and the second port 64 do not communicate with the third
port 65.
[0120] Since the coolant does not flow into the radiator passage
53, the coolant will not be cooled by the radiator 27. Therefore,
the coolant rises promptly in the temperature. Further, the
combustion chamber 16 is not cooled by the circulation of the
coolant. The combustion chamber 16 can be promptly heated by the
combustion heat. Since the engine 10 promptly rises to the
temperature state suitable for combustion, fuel efficiency can be
improved. At this time, the coolant discharged from the water pump
3 circulates through the second circuit 30 and the third circuit
40.
[0121] As illustrated by a center state 82 in FIG. 6, during "Half
Warm-up," although the coolant flows into the bypass passage 51,
the coolant does not flow into the radiator passage 53 (the flow
rate of the radiator passage 53 is zero). That is, in the first
circuit 50, the coolant only circulates through the bypass passage
51. At this time, in the coolant control valve 4, the rotary valve
body 61 is set at a rotational position where only the first port
63 communicates with the third port 65. The opening of the first
water flow opening 61a is fully open, for example.
[0122] Since the coolant does not flow into the radiator passage
53, the coolant promptly rises in the temperature. On the other
hand, since the coolant flows into the bypass passage 51, the
coolant flows into the first jacket 22a. The bypass passage 51 is
short. Further, since the coolant control valve 4 is set to be
fully opened, most of the coolant flows through the bypass passage
51 and the first jacket 22a.
[0123] The combustion chamber 16 can be promptly heated by the
circulating coolant. Since the coolant is circulated, the
combustion chamber 16 and its circumference can be heated
uniformly. Since the engine 10 promptly rises to the temperature
state suitable for combustion, fuel efficiency can be improved.
[0124] Note that, at this time, the remainder of the coolant
discharged from the water pump 3 circulates through the second
circuit 30 and the third circuit 40 (similar during "Full
Warm-up"). The temperature of the coolant during "Half Warm-up" is
lower than the valve-opening temperature of the thermally-actuated
valve 28. Therefore, the thermally-actuated valve 28 is in a fully
closed state. Part of the coolant will not flow into the radiator
passage 53 from the bypass passage 51.
[0125] During "Full Warm-up," the engine 10 reaches the temperature
state suitable for combustion. The engine 10 after fully warmed up
changes the combustion mode according to the load and the engine
speed, as described above. This engine system 1 controls the
circulation system 91 so that the wall temperature of the
combustion chamber 16 becomes a temperature suitable for the
combustion mode. During "Full Warm-up," the state 82 illustrated in
the center of FIG. 6 and a state 83 illustrated in the right of
FIG. 6 are switched according to the operating state of the engine
10. The state 82 is a state where the bypass passage 51 is opened
and the radiator passage 53 is closed, as described above. However,
since the temperature of the coolant rises during "Full Warm-up,"
the coolant may flow through the radiator passage 53 by the
thermally-actuated valve 28 being opened, as will be described
later. The state 83 is a state where the circulation of the coolant
is performed using the entire first circuit 50 by opening both the
bypass passage 51 and the radiator passage 53.
[0126] In more detail, during "Full Warm-up," as illustrated by the
center state 82, in the coolant control valve 4, the rotary valve
body 61 is set at a rotational position so that the first port 63
communicates with the third port 65, and the second port 64 does
not communicate with the third port 65. Further, according to the
load of the engine 10, the flow rate of the coolant is adjusted at
the first port 63 (bypass passage 51).
[0127] During "Full Warm-up," as illustrated by the right state 83,
the coolant flows into both the bypass passage 51 and the radiator
passage 53. In that case, in the coolant control valve 4, the
rotary valve body 61 is set at a rotational position so that both
the first port 63 and the second port 64 communicate with the third
port 65. Further, according to the load of the engine 10, the flow
rate of the coolant is adjusted at both the first port 63 (bypass
passage 51) and the second port 64 (radiator passage 53).
(How Coolant Flows When Fully Warmed Up)
[0128] FIG. 7 illustrates a concrete example of how the coolant
flows when fully warmed up. In FIG. 7, charts (A) to (D) illustrate
changes in main properties according to the load of the engine
10.
[0129] Chart (A) illustrates change G1 in the flow rate of the
coolant which passes through the coolant control valve 4, and
change G2 in the flow rate of the coolant which passes through the
radiator passage 53. Chart (B) illustrates the details of the
change in the flow rate of the coolant which flows through the
first circuit 50, that is, change G3 in the flow rate of the
coolant which flows into the bypass passage 51 from the coolant
control valve 4, change G4 in the flow rate of the coolant which
flows through the connecting passage 52, and change G5 in the flow
rate of the coolant which flows into the radiator passage 53 from
the coolant control valve 4.
[0130] Chart (C) illustrates change G6 in the temperature of the
coolant which flows through the first jacket 22a, and change G7 in
the temperature of the coolant which flows into the water pump 3.
In other words, changes in the measurements of the second water
temperature sensor SN2 and the first water temperature sensor SN1
are illustrated. Chart (D) illustrates change G8 in the wall
temperature of the combustion chamber 16.
[0131] The load range of the engine 10 is divided, in association
with the control of the coolant, into three ranges comprised of a
range below the first load L1, a range above the second load L2,
and a range above the first load L1 and below the second load L2.
Each chart of FIG. 7 corresponds to the case where the engine speed
of the engine 10 is the low speed or the middle speed. The range
below the first load L1 is a range where the engine 10 performs
HCCI combustion or MPCI combustion. The range above the second load
L2 is a range where the engine 10 performs SI combustion. The range
above the first load L1 and below the second load L2 is a range
where the engine 10 performs SPCCI combustion.
[0132] Further, in this engine system 1, the flow rate control of
the coolant is performed in the range where the engine 10 performs
HCCI combustion or MPCI combustion, and the temperature control of
the coolant is performed in the range where the engine 10 performs
SPCCI combustion. The range where the engine 10 performs HCCI
combustion or MPCI combustion is, in other words, a range where the
air-fuel mixture combusts without forcible ignition of the spark
plug 132, and the range where the engine 10 performs SPCCI
combustion is a range where the air-fuel mixture combusts by the
forcible ignition of the spark plug 132.
[0133] The engine system 1 maintain the wall temperature of the
combustion chamber 16 at the specific constant temperature in the
ranges where the load of the engine 10 is low and middle by
switching between the flow rate control and the temperature control
(see G8).
[0134] That is, in order to realize the compression self-ignition
combustion without forcible ignition, like HCCI combustion or MPCI
combustion, it is necessary to accurately control the temperature
inside the combustion chamber 16 (in-cylinder temperature) at a
temperature higher than SI combustion. On the other hand, SPCCI
combustion is combustion accompanied by forcible ignition though
part of the air-fuel mixture combusts by compression ignition, and
the temperature inside the combustion chamber 16 is permitted to be
lower than that of HCCI combustion or MPCI combustion. On the
contrary, if the temperature inside the combustion chamber 16 is
too high, the air-fuel mixture may carry out self-ignition before
forcible ignition is performed, or a rate of the self-ignition
combustion may become too large in the SPCCI combustion where flame
propagation combustion and self-ignition combustion are combined.
That is, if the temperature inside the combustion chamber 16 is too
high, stable SPCCI combustion will not be realized.
[0135] Therefore, it is ideal to change the wall temperature of the
combustion chamber 16 according to the switching of the combustion
mode. However, since the calorific capacity of the wall part of the
combustion chamber 16 is large, it is difficult to change the wall
temperature of the combustion chamber 16 with sufficient response
to the switching of the combustion mode or the change in the load.
Thus, in the range from the low load to the middle load, the engine
system 1 maintains the wall temperature of the combustion chamber
16 at the specific constant temperature. This specific temperature
is an intermediate temperature between an optimal temperature for
HCCI combustion or MPCI combustion and an optimal temperature for
SPCCI combustion, is a temperature permissible in the execution of
HCCI combustion or MPCI combustion, and is a temperature also
permissible in the execution of SPCCI combustion. Even if the
combustion mode is switched or the load is changed, the wall
temperature of the combustion chamber 16 becomes a suitable
temperature by maintaining the wall temperature of the combustion
chamber 16 at the constant temperature.
[0136] However, if the load of the engine 10 is low, the combustion
heat increases in general, and if the load of the engine 10
increases, the combustion heat decreases in general. In order to
maintain the constant wall temperature of the combustion chamber 16
regardless of the load of the engine 10, it is necessary to adjust
the heat exchanging quantity by the coolant with high response to
the occurring combustion heat.
[0137] For example, in order to adjust the heat exchanging
quantity, it is possible to adjust the temperature of the coolant
according to the load of the engine 10. However, since the
calorific capacity of the coolant is large, it requires a long
period of time to raise or lower the temperature of the coolant. It
is difficult to adjust the temperature of the coolant with high
response to the change in the load of the engine 10.
[0138] Thus, this engine system 1 adjusts the flow rate of the
coolant which flows through the first port 63 and the first jacket
22a by using the coolant control valve 4 according to the load of
the engine 10, while keeping the temperature of the coolant
constant at a given temperature. Since the adjustment of the flow
rate can be changed with high response, the heat transfer
coefficient by the coolant can be adjusted with high response
against the occurring combustion heat, and, as a result, the wall
temperature of the combustion chamber 16 can be maintained
constant.
(Range of HCCI Combustion or MPCI Combustion)
[0139] As illustrated in FIG. 7, in the range where HCCI combustion
or MPCI combustion is performed, the coolant control valve 4
adjusts the flow rate of the coolant which flows through the bypass
passage 51 without the coolant flowing to the radiator passage 53
(see G3, G5).
[0140] Since the radiator passage 53 is closed, the temperature of
the coolant is determined by a valve-opening temperature of the
thermally-actuated valve 28. The valve-opening temperature of the
thermally-actuated valve 28 is set at a comparatively high
temperature. The temperature of the coolant which flows through the
first jacket 22a is constant at a first target temperature t21,
regardless of the load (see G6). The first target temperature t21
is a temperature near the reliability limit temperature of the
engine 10. By setting the temperature of the coolant at the
comparatively high temperature, in the range where HCCI combustion
or MPCI combustion is performed, the wall temperature of the
combustion chamber 16 can be maintained at the comparatively high
temperature (that is, a target temperature tw). When the wall
temperature of the combustion chamber 16 is high, it is
advantageous to stabilize the compression self-ignition combustion
without forcible ignition like HCCI combustion or MPCI combustion.
Note that, in the example of the drawing, in the range below the
first load L1, the temperature of the coolant which flows into the
engine 10 gradually rises as the load of the engine 10 increases
(see G7).
[0141] In the range where HCCI combustion or MPCI combustion is
performed, the coolant control valve 4 adjusts the flow rate so
that the flow rate of the coolant which flows through the bypass
passage 51 becomes less when the load of the engine 10 is low, and
the flow rate of the coolant which flows through the bypass passage
51 becomes more when the load of the engine 10 is high.
[0142] At this time, in the coolant control valve 4, the actuator
62 is controlled so that the rotary valve body 61 is located at a
rotational position where the third port 65 does not communicate
with the second port 64 and the third port 65 communicates with the
first port 63. Further, according to the load of the engine 10, the
opening between the third port 65 and the first port 63 is
adjusted.
[0143] Note that, in the range where HCCI combustion or MPCI
combustion is performed, the flow rate of the coolant which flows
through the connecting passage 52 when the thermally-actuated valve
28 is opened changes corresponding to the change in the flow rate
of the coolant which flows through the bypass passage 51 (see
G4).
[0144] Here, in the example of the drawing, although the load of
the engine 10 and the flow rate of the coolant have a linear
relationship, it is not limited to the linear relationship.
[0145] The flow rate of the coolant which flows through the first
jacket 22a corresponds to the flow rate of the coolant which flows
through the bypass passage 51. Therefore, when the load of the
engine 10 is low, the flow rate of the coolant which flows through
the first jacket 22a is small, and when the load of the engine 10
is high, the flow rate of the coolant which flows through the first
jacket 22a is large. In the example of FIG. 7, when the load of the
engine 10 is the first load L1, the flow rate of the coolant which
flows through the first jacket 22a becomes the maximum flow rate
(see G1). Note that when the load of the engine 10 is the first
load L1, the flow rate of the coolant which flows through the first
jacket 22a may be below the maximum flow rate.
[0146] When the flow rate of the coolant which flows through the
first jacket 22a is small, the heat transfer coefficient with the
combustion chamber 16 falls. Therefore, even if the combustion heat
decreases, the wall temperature of the combustion chamber 16 can be
adjusted to a high temperature. When the flow rate of the coolant
which flows through the first jacket 22a is large, the heat
transfer coefficient with the combustion chamber 16 increases.
Therefore, even if the combustion heat increases, the wall
temperature of the combustion chamber 16 can be adjusted to a low
temperature.
[0147] In this way, while maintaining the temperature of the
coolant constant by using the thermally-actuated valve 28 (see G6),
the flow rate of the coolant which flows through the first jacket
22a is fluctuated using the coolant control valve 4 with high
response according to the load of the engine 10 (see G1, G3).
Therefore, the wall temperature of the combustion chamber 16 can be
held constant at the target temperature tw (see G8).
(Range of SPCCI Combustion)
[0148] The flow rate of the coolant which flows through the coolant
control valve 4 (i.e., the flow rate of the coolant which flows
through the first circuit 50) reaches an upper limit at the first
load L1 (see G1). That is, the flow rate control cannot be
performed at the load above the first load L1. Thus, in the range
above the first load L1 and below the second load L2, the
temperature control of the coolant is performed. The wall
temperature of the combustion chamber 16 is held at the target
temperature tw by gradually allowing the coolant which flows
through the bypass passage 51 to flow to the radiator passage 53 as
the load of the engine 10 increases, to cool the coolant.
[0149] In detail, in a state where the flow rate of the coolant
which flows through the first circuit 50 is held at the maximum
flow rate, the coolant control valve 4 gradually increases the flow
rate of the coolant which flows through the radiator passage 53,
while gradually reducing the flow rate of the coolant which flows
through the bypass passage 51, as the load of the engine 10
increases (see G1, G2, G3, G5). In the range of SPCCI combustion,
the coolant control valve 4 adjusts the temperature of the coolant
which flows through the first jacket 22a by adjusting the flow rate
of the coolant which flows through the radiator passage 53. Note
that if the load of the engine 10 is above the first load L1, the
flow rate of the coolant which flows through the radiator passage
53 exceeds the flow rate of the coolant which flows through the
bypass passage 51. The load of the engine 10 at which the flow rate
is reversed changes according to the operating environments of the
engine 10 (for example, ambient temperature, wind quantity during
the vehicle traveling, etc.).
[0150] The coolant control valve 4 controls the actuator 62 so that
the rotary valve body 61 is located at a rotational position where
the third port 65 communicates with both the first port 63 and the
second port 64. Further, according to the load of the engine 10,
the opening between the third port 65 and each of the first port 63
and the second port 64 is adjusted.
[0151] Thus, the temperature of the coolant which flows through the
first jacket 22a and the temperature of the coolant which flows
into the engine 10 become lower as the load of the engine 10
increases (see G6, G7). When the load of the engine 10 increases to
increase the combustion heat, since the temperature of the coolant
which flows through the first jacket 22a is low even if the flow
rate of the coolant is constant, the cooling quantity by the
coolant which flows through the first jacket 22a can be maintained.
Further, since the flow rate of the coolant which flows through the
first circuit 50 is the maximum flow rate, it is advantageous to
cool the combustion chamber 16. As a result, also in the range of
SPCCI combustion, the wall temperature of the combustion chamber 16
can be held at the target temperature tw (see G8).
[0152] In order to suppress the excessive rise in the temperature
of the combustion chamber 16, in this cooling system, a second
target temperature t22 (for example, 88.degree. C.) lower than the
first target temperature t21 is set as a target temperature of the
coolant which flows through the first jacket 22a. The temperature
control is performed until the temperature of the coolant which
flows through the first jacket 22a reaches the second target
temperature t22.
[0153] Note that, as illustrated in G5 of FIG. 7, when the
temperature of the coolant reaches the second target temperature
t22, the flow rate of the coolant which flows through the radiator
passage 53 is below the maximum flow rate. If the flow rate of the
coolant which flows through the radiator passage 53 is further
increased, the temperature of the coolant can be further reduced.
That is, even if the load of the engine 10 exceeds L2, it is
possible to maintain the wall temperature of the combustion chamber
16 at the target temperature tw.
[0154] Thus, the engine system 1 can maintain the wall temperature
of the combustion chamber 16 constant over the wide range from the
low load to the middle load of the engine 10, by the combination of
the flow rate control and the temperature control. Since the wall
temperature of the combustion chamber 16 is maintained at the
suitable temperature even if the combustion mode is switched
between HCCI combustion, MPCI combustion, and SPCCI combustion
corresponding to the change in the load of the engine 10, each
combustion is stably performed.
[0155] The coolant control valve 4 having the rotary valve body 61
can selectively close the bypass passage 51 and/or the radiator
passage 53, and can adjust the flow rate of the bypass passage 51
and the flow rate of the radiator passage 53. The engine system 1
provided with the coolant control valve 4 can realize the flow rate
adjustment of the water jacket 20 described above with the simple
configuration.
[0156] Note that, in the range of SPCCI combustion, the coolant
which flows into the radiator passage 53 through the connecting
passage 52 gradually decreases and will not flow as the load of the
engine 10 increases (see G4). In detail, the temperature of the
coolant which flows into the bypass passage 51 from the coolant
control valve 4 gradually decreases from the first target
temperature t21. In connection with it, the temperature of the
coolant which flows through the thermally-actuated valve 28 also
decreases. Therefore, in the range of SPCCI combustion, the
thermally-actuated valve 28 gradually closes, and it will become
fully closed. Therefore, the coolant which flows into the radiator
passage 53 through the connecting passage 52 gradually decreases,
and will not flow.
[0157] Although in the example of FIG. 7 a proportional
relationship exists between the flow rate reduction of the coolant
which flows through the bypass passage 51 and the flow rate
increase of the coolant which flows through the radiator passage
53, there is no necessity of being the proportional relationship.
In the range of SPCCI combustion, the flow rate of the coolant
which flows through the coolant control valve 4 may be below the
upper limit.
(Range of SI Combustion)
[0158] In the range of SI combustion, the adjustment is performed
in the coolant control valve 4 so that the temperature of the
coolant which flows through the first jacket 22a is held at the
second target temperature t22. In detail, the actuator 62 is
controlled, and the adjustment is made so that the opening between
the third port 65 and the second port 64 becomes large, and the
opening between the third port 65 and the first port 63 becomes
small, as the load of the engine 10 increases. Thus, the coolant
which flows through the radiator passage 53 gradually increases,
and the coolant which flows through the bypass passage 51 gradually
decreases (see G3, G5). By doing so, the temperature of the coolant
which flows through the first jacket 22a can be held at the second
target temperature t22 (see G6).
[0159] In the range where SI combustion is performed, it becomes
possible to suppress abnormal combustion, such as knocking, by
relatively lowering the temperature of the coolant.
[0160] In the range of SPCCI combustion (in other words, the range
above the first load L1 and below the second load L2), in order to
maintain the wall temperature of the combustion chamber 16
constant, the temperature of the coolant which flows through the
first jacket 22a is positively lowered as the load of the engine 10
increases. Therefore, with respect to the increase in the load of
the engine 10, a degree of change in the flow rate of the coolant
which flows into the bypass passage 51 from the coolant control
valve 4, and a degree of change in the flow rate of the coolant
which flows into the radiator passage 53 from the coolant control
valve 4 are relatively large. That is, slopes of G3 and G5 are
larger.
[0161] On the other hand, in the range of SI combustion (in other
words, the range above the second load L2), in order to hold the
temperature of the coolant at the second target temperature t22,
with respect to the increase in the load of the engine 10, a degree
of change in the flow rate of the coolant which flows into the
bypass passage 51 from the coolant control valve 4, and a degree of
change in the flow rate of the coolant which flows into the
radiator passage 53 from the coolant control valve 4 are relatively
small. That is, the slopes of G3 and G5 are small, and the slopes
of G3 and G5 change at the second load L2.
[0162] Note that in the range of SI combustion (in other words, the
range above the second load L2), the proportional relationship
between the flow rate reduction of the coolant which flows through
the bypass passage 51 and the flow rate increase of the coolant
which flows through the radiator passage 53 is not essential. In
the range of SI combustion, the flow rate of the coolant which
flows through the coolant control valve 4 may be below the upper
limit.
[0163] In the range of SI combustion, the flow rate of the coolant
which flows through the first jacket 22a is the maximum, and the
temperature of the coolant is held at the second target temperature
t22. Since the heat occurring inside the combustion chamber 16
increases as the load of the engine 10 increases, the wall
temperature of the combustion chamber 16 gradually rises as the
load of the engine 10 increases (see G8).
[0164] Note that in the range of SI combustion, since the
temperature of the coolant is maintained at the second target
temperature t22, the thermally-actuated valve 28 is fully closed.
The coolant does not flow into the connecting passage 52. The
bypass passage 51 and the radiator passage 53 constitute mutually
independent passages.
[0165] Next, a control executed by the ECU 100 for cooling of the
engine 10 is described with reference to FIGS. 8 and 9.
[0166] FIG. 8 is a flowchart for switching between a cold state, a
half warmed up state, and a fully warmed up state of the engine 10.
First, at Step S81 after the start, the ECU 100 acquires signal
values outputted from various kinds of the sensors SN1-SN5. The
subsequent Step S82, the ECU 100 determines whether the temperature
t of the coolant is at or above the second switching temperature
t12 based on the signal from the second water temperature sensor
SN2. If the temperature t of the coolant is at or above the second
switching temperature t12, the process shifts from Step S82 to Step
S83. At Step S83, the ECU 100 executes a full warm-up control. The
details of the full warm-up control is described with reference to
FIG. 9.
[0167] If the temperature of the coolant is below the second
switching temperature t12, the process shifts from Step S82 to Step
S84. At Step S84, the ECU 100 determines whether the temperature t
of the coolant is at or above the first switching temperature t11.
If the temperature t of the coolant is at or above the first
switching temperature t11, the process shifts from Step S84 to Step
S85. At Step S85, the ECU 100 executes a half warm-up control. As
described above, the ECU 100 opens the bypass passage 51 and closes
the radiator passage 53, through the coolant control valve 4.
[0168] If the temperature t of the coolant is below the first
switching temperature t11, the process shifts from Step S84 to Step
S86. At Step S86, the ECU 100 executes a low-temperature control.
As described above, the ECU 100 closes the bypass passage 51 and
closes the radiator passage 53, through the coolant control valve
4.
[0169] FIG. 9 illustrates a flow of the full warming-up control at
Step S83. At Step S91 after the start, the ECU 100 calculates a
target load of the engine 10 based on the signal values outputted
from the sensors SN1-SN5. At the subsequent Step S92, the ECU 100
determines whether the combustion mode is HCCI combustion or MPCI
combustion based on the target load L. If the determination at Step
S92 is YES, the process shifts from Step S92 to Step S93. At Step
S93, the ECU 100 executes the flow rate control. That is, the ECU
100 closes the radiator passage 53 and adjusts the flow rate of the
bypass passage 51 according to the load of the engine 10, through
the coolant control valve 4.
[0170] If the combustion modes are not HCCI combustion and MPCI
combustion, the process shifts from Step S92 to Step S94. At Step
S94, the ECU 100 determines whether the combustion mode is SPCCI
combustion based on the target load L. If the determination at Step
S94 is YES, the process shifts from Step S94 to Step S95. At Step
S95, the ECU 100 executes the temperature control. That is, the ECU
100 adjusts the flow rates of the radiator passage 53 and the
bypass passage 51 through the coolant control valve 4 according to
the load of the engine 10 so that the wall temperature of the
combustion chamber 16 becomes constant.
[0171] If the combustion mode is SI combustion, the process shifts
from Step S94 to Step S96. At Step S96, the ECU 100 adjusts the
flow rates of the radiator passage 53 and the bypass passage 51
through the coolant control valve 4 according to the load of the
engine 10 so that the temperature of the coolant becomes
constant.
(Modification of Circulation System)
[0172] FIG. 10 illustrates a circulation system 92 according to a
modification. This circulation system 92 differs from the
circulation system 91 of FIG. 4 in the position of the
thermally-actuated valve 28.
[0173] In detail, the thermally-actuated valve 28 is attached to
the outflow-side end part 10b of the engine 10, instead of the
bypass passage 51. A downstream end of the first jacket 22a
provided to the cylinder head 12 branches into two. The coolant
control valve 4 and the thermally-actuated valve 28 are connected
to the first jacket 22a.
[0174] The thermally-actuated valve 28 is connected by the radiator
passage 53 via the connecting passage 52. In more detail, the
connecting passage 52 is connected to a part of the radiator
passage 53 upstream of the radiator 27.
[0175] Note that this circulation system 92 does not have the
connecting passage which connects the bypass passage 51 to the
radiator passage 53 in the circulation system 91 of FIG. 4.
[0176] How the coolant flows in the circulation system 92 is the
same as the circulation system 91 of FIG. 4. That is, if the
temperature t of the coolant is in "Low Temperature" state below
the first switching temperature t11, the coolant neither flows into
the bypass passage 51 nor the radiator passage 53 (both the flow
rates are zero). At this time, in the coolant control valve 4, the
rotary valve body 61 is set at the rotational position where both
the first port 63 and the second port 64 do not communicate with
the third port 65. Further, the thermally-actuated valve 28 is
closed. Therefore, in the first circuit 50, the circulation of the
coolant is not performed.
[0177] If the temperature t of the coolant is in "Half Warm-up"
state at or above the first switching temperature t11 and below the
second switching temperature t12, although the coolant flows to the
bypass passage 51, it does not flow to the radiator passage 53 (the
flow rate of the radiator passage 53 is zero). At this time, in the
coolant control valve 4, the rotary valve body 61 is set at the
rotational position where only the first port 63 communicates with
the third port 65. The opening of the first water flow opening 61a
is fully open, for example. Further, since the temperature of the
coolant is low, the thermally-actuated valve 28 is closed. In the
first circuit 50, the circulation of the coolant is performed only
in the bypass passage 51.
[0178] If the temperature t of the coolant is in "Ful Warm-up"
state at or above the second switching temperature t12, the
circulation system 92 is controlled according to the change of the
combustion mode.
[0179] Concretely, when the operating state of the engine 10 is in
the range of HCCI combustion or MPCI combustion, the flow rate
control is performed. The temperature of the coolant is kept
constant by the thermally-actuated valve 28. The coolant control
valve 4 opens the bypass passage 51 and closes the radiator passage
53. Note that the coolant may pass through the radiator 27 by the
thermally-actuated valve 28 being opened. The coolant control valve
4 adjusts the flow rate of the coolant which flows through the
bypass passage 51 according to the load of the engine 10.
Therefore, the wall temperature of the combustion chamber 16 is
maintained at the target temperature tw.
[0180] The temperature control is performed when the operating
state of the engine 10 is in the range of SPCCI combustion and
below the second load L2. The coolant control valve 4 opens both
the bypass passage 51 and the radiator passage 53. In more detail,
the coolant control valve 4 reduces the flow rate of the coolant
which flows through the bypass passage 51 and increases the flow
rate of the coolant which flows through the radiator passage 53, as
the load of the engine 10 increases. Therefore, the wall
temperature of the combustion chamber 16 is maintained at the
target temperature tw.
[0181] When the operating state of the engine 10 is in the range of
SI combustion, the coolant control valve 4 adjusts the flow rates
of the coolant which flows through the bypass passage 51 and the
radiator passage 53 so that the temperature t of the coolant
becomes constant at the second target temperature t22. In more
detail, the coolant control valve 4 reduces the flow rate of the
coolant which flows through the bypass passage 51 and increases the
flow rate of the coolant which flows through the radiator passage
53, as the load of the engine 10 increases. The thermally-actuated
valve 28 is closed.
[0182] Since the engine system 1 provided with the circulation
system 92 performs the flow rate control in the range of HCCI
combustion or MPCI combustion, it can change the flow rate of the
coolant which flows through the first jacket 22a with high response
to the load of the engine 10 changing, and can keep the wall
temperature of the combustion chamber 16 constant.
[0183] Further, since the wall temperature of the combustion
chamber 16 can be maintained at the target temperature tw by
performing the temperature control in the range of SPCCI
combustion, even if the combustion mode of the engine 10 is
switched between HCCI combustion, MPCI combustion, and SPCCI
combustion, the wall temperature of the combustion chamber 16 does
not change. The HCCI combustion and MPCI combustion without
forcible ignition can be performed stably, and the SPCCI combustion
accompanied by forcible ignition can also be performed stably.
[0184] The circulation system 92 does not provide the
thermally-actuated valve 28 to downstream of the coolant control
valve 4. The connecting passage 52 is a passage which bypasses the
coolant control valve 4. For this reason, even if the coolant
control valve 4 has failed, such as valve adhesion, the
thermally-actuated valve 28 can be opened to cool the coolant by
the radiator 27 when the temperature of the coolant reaches the
valve-opening temperature of the thermally-actuated valve 28. Since
the circulation system 92 can suppress that the temperature of the
coolant becomes excessively high, it is advantageous to improve the
reliability of the engine system 1.
Other Embodiments
[0185] Note that in the circulation system 91 of FIG. 4, the
position of the coolant control valve 4 may be changed. In detail,
the coolant control valve 4 may be provided at a location where the
bypass passage 51 and the radiator passage 53 join (a location
surrounded by a one-dot chain line of FIG. 4). In this
configuration, the upstream end of the bypass passage 51 and the
upstream end of the radiator passage 53 are connected
mutually-independently to the first jacket 22a. Further, the
connecting passage 52 may connect the bypass passage 51 to a
location of the radiator passage 53 downstream of the radiator 27,
and the thermally-actuated valve 28 may be provided so as to open
and close the connecting passage 52.
[0186] Similarly, in the circulation system 92 of FIG. 10, the
position of the coolant control valve 4 may be changed. In detail,
the coolant control valve 4 may be provided at a location where the
bypass passage 51 and the radiator passage 53 join (a location
surrounded by a one-dot chain line of FIG. 10). In this
configuration, the upstream end of the bypass passage 51 and the
upstream end of the radiator passage 53 are connected
mutually-independently to the first jacket 22a. Further, the
connecting passage 52 may connect a part of the radiator passage 53
downstream of the radiator 27 and a part upstream of the water pump
3 so as to bypass the coolant control valve 4, and the
thermally-actuated valve 28 may be provided so as to open and close
the connecting passage 52.
[0187] Further, the flow rate control device is not limited to be
comprised of the coolant control valve 4 having the rotary valve
body 61. The flow rate control device may be comprised of a first
flow rate control valve which adjusts the flow rate of the coolant
which flows through the bypass passage 51, and a second flow rate
control valve which adjusts the flow rate of the coolant which
flows through the radiator passage 53 and is independent from the
first flow rate control valve.
[0188] FIG. 3 illustrates one example of the control of the engine
system 1. The switching of the combustion mode is not limited to
the example of FIG. 3.
[0189] It should be understood that the embodiments herein are
illustrative and not restrictive, since the scope of the invention
is defined by the appended claims rather than by the description
preceding them, and all changes that fall within metes and bounds
of the claims, or equivalence of such metes and bounds thereof, are
therefore intended to be embraced by the claims.
DESCRIPTION OF REFERENCE CHARACTERS
[0190] 1 Engine System [0191] 10 Engine [0192] 16 Combustion
Chamber [0193] 100 ECU (Controller) [0194] 132 Spark Plug [0195]
22a First Jacket (Water Jacket) [0196] 27 Radiator (Heat Exchanger)
[0197] 28 Thermally-actuated Valve [0198] 4 Coolant Control Valve
(Flow Rate Control Device) [0199] 51 Bypass Passage [0200] 52
Connecting Passage [0201] 53 Radiator Passage [0202] 91 Circulation
System [0203] 92 Circulation System
* * * * *